


My One and Only Ruler

by skepticallysighing



Category: Undertale (Video Game)
Genre: Angst, Bad Puns, Chef Papyrus, Crossdressing, Eventual Smut, Fluff, Longing, Love, M/M, Masturbation, One Sided Love, Sans Remembers Resets, jester!sans, king!mettaton, royal guard!papyrus, trombone, underkeep
Language: English
Status: In-Progress
Published: 2016-06-08
Updated: 2016-07-18
Packaged: 2018-07-13 20:52:48
Rating: Mature
Warnings: Major Character Death
Chapters: 4
Words: 3,705
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7136657
Author URL: https://archiveofourown.org/users/skepticallysighing/pseuds/skepticallysighing
Summary: <blockquote class="userstuff">
              <p>Underkeep is an AU where Asgore steps down from being King due to a depression, and Mettaton takes his place. The outfits of the au are gorgeous, but beauty only exists here to hide the true hidden suffering.</p><p>More specifically, a jester finds himself in love with his master, the king. And he doesn't know how to tell him. But perhaps he'll take his own steps to have the king for himself...</p><p>Also, for those of you who didn't just get that, SANS IS YANDERE FOR METTATON AND IS GOING TO CUT SOME BITCHES UP.</p>
            </blockquote>





	1. Longing

Mettaton never really saw Sans a lot. The two were simply so different, and they kept to their own worlds. Mettaton belonged on the television, at parties, talking to fans and being interviewed while wearing his designer pink gown. Sans just stood there eating everything, occasionally glancing at his king.

The king could never understand that about his jester. Around him, the skeleton was so eager to please, dancing and juggling and telling jokes. Yet in the crowds, he didn’t seem to know Mettaton.

But honestly, why was Metta thinking about that little skeleton so much? He had to focus on rehearsing for his show, where he’d sing a beautiful human melody and act out a fantastic scene. His character was fascinating and it was such an honour to play him.

Though the costumes were the best. He got to sing in a loose white gown that spread out like a wedding dress, white flowers weaved into his black hair. He looked quite nice in it truthfully.

He was thrilled for the practice. Tonight was the night they’d begin to practice with the stage, doing run throughs of the show. It was better than listening to prerecorded music, today, the royal band would be here, thank god.

“Your majesty?” murmured a soft voice, and Metta looked back. A ghostie with a little crown and a long blue cloak. 

“Napstablook, darling~” Mettaton cooed, rising to his feet and walking forward. The gown clung to his body just right, and he moved like a dancer. “What is it?”

Prince Napstablook looked away shyly, mumbling: “I-I...um...Sh-Shyren’s gotten her melodies down and we’re ready to start practicing.”

“Ah? Alright. I’ll be down in just a second, darling,” Mettaton hummed, looking away and continuing to fix up his makeup. With just some white on the inner corners, just some white between his lashes and his eye, a slim line of black over the top and a flash of mascara...and just out of the corner of his eye stood he.

A blue shirt with a black vest over it, puffed sleeves and black gloves. A ruffle of pink around his neck that matched the ribbon around his top hat. A blue feather billowed from the hatin question. And the wearer of such fine clothes leaned against the door, smirking. And right beside him was the taller skeleton, who wore golden gloves and white-gold armour, his billowing red cloak flying behind him despite there being no wind. He plays with his flame sword, smiling brightly.

“Mettaton, hello! I just came here with S-”

“Hey, tin can. You missed the rehearsal again.” He pulled out his trombone and went wan wan waaaan to add an effect.

Mettaton groaned, rising up and stepping forward. “I did..? Shit. I guess I got so distracted.” There was quite the difference in height. With his heels, Metta was seven feet tall in comparison to Sans’s four feet and Papyrus’s five-seven.

“Sans, you can’t just call the king a tin can! You’re so brash!” Pap scolded.

“That’s me,” Sans winked, not abashed at all. “What do you call a man who knows how to play the trombone but doesn’t?”

The king set his hands on his hips. “I don’t know.”

“Sans d-”

“A gentleman.”

“SANS!”

_ Wan wan waaaaan. _

Mettaton felt pity for Papyrus having to put up with this squat skelly Sans.

“If you keep that up, you’re not going to get tromboned tonight~”

This made both skeleton’s blush, and Papyrus exclaimed: “I AM LEAVING! THE GREAT PAPYRUS DOES NOT NEED TO HEAR ANY OF THIS!” And he did indeed leave, cape flapping behind him.

Sans laughed and looked back at Mettaton, closing the door. “So...you wanna practice together, your majesty?”

Mettaton smiled. “Of course.” He sat on the bed. “Come sit beside me~”

“Actually, I’ll be in the pit, so we can practice distance.” He stood by the door, grinning cheekily.

The king sighed dramatically. “Sans, can’t you just come over here?”

“But I’m already all the way over here, I might wear myself out. I’d have to make one trip to move the trombone and another trip to bring the sheet music. Would you really make me suffer like that?”

“You’re the laziest royal jester there ever was.”

“Thank you, beautiful prince~”

That was another thing. He never called him beautiful or prince or majesty when they were in public. Only when they were alone together.

But when they played together, it was beautiful. A bit odd, the rich Italian coming off Metta’s lips with the slide of the trombone. And odd combo of course, but together it seemed like there was not a better way to do it.

Papyrus is what interrupted them, peeking his head in. “King Mettaton, dinner is ready, Muffet and I made a dish you’re sure to love! Nyeh heh heh! Would you like to come downstairs or stay here?”

“I’ll come down,” he hums softly, glancing at Sans. “Are you going to join me?”

Papyrus spluttered at this.

Sans grinned. “Na. Wouldn’t wanna crash your fancy dinner. And I gotta keep an eye on my bro.”

“Alright. At least help me change out of my gown,” he winked. Papyrus quickly closed the door, blushing.

In truth, there was no real love to Sans and Mettaton’s relationship. They never had sex, they never kissed, and neither would confess feelings. Sans didn’t blush as he helped Metta change, and Metta felt no embarrassment as he was changed.

Sans sang sometimes. Mettaton didn’t understand the language, but that didn’t stop him from listening. When everyone thought the two were having sex, Mettaton was just curling up in the bed, Sans holding his hand gently, playing with it silently. When he saw the normally arrogant king fast asleep, so content, so peaceful...he felt so happy.

At times like this, Sans would reach out and touch his king’s face before leaning in. He never kissed the prince, fearing that the beautiful robot would awaken if he did. But he inhaled the soft perfume that was distinctly Mettaton. He would smile and lean back, bringing the palm to his lips and kissing it.

“I love you more than anything,” he would whisper when he knew the king was asleep. There was no chance of rejection when the king was asleep...he stayed there all night, quietly watching him.

He's not lazy all the time. He's just tired from always watching his beautiful king.

It's only when the sun starts to rise that Sans stands up and turns away, quietly closing the door behind him.


	2. Lust

When rehearsal was done again, Mettaton changed out of his outfit. Since Papyrus was busy that day, Sans was appointed with cleaning the fancy clothes up. He quietly took the dress, walking down to wash it, though he secretly wanted to keep it. Under his mattress where he could reach under it and finger the soft cloth, imagine Mettaton’s sexy curved body filling it out. But he knew how disgusting that was and made himself keep carrying it.

And now he was sitting on the ground beside the washing machine, door locked, leaning against the wall as he looked over the gown. Robots didn’t have scents, they were just metal, yet this dress smelled like that perfume that was distinctly Mettaton.

He pressed it to his face, sniffing it, damn that smelled nice...he rubbed his face in the cloth, loving that delicious scent. If only he could keep the dress and smell it forever. Did Metta smell like this? Sweet and...addictive?

After a few more seconds of rubbing the dress all over his face and huffing it, a thought sparked into his mind. Could he…

No. He c-couldn’t do  _ that _ .

But he still set the dress in his lap and picked up one of Mettaton’s socks. A silky white sock, molded to shape the king’s slim legs, stretched from his toes and his ankle, his calves...Sans didn’t have a foot fetish, but holding the stocking, knowing that Mettaton had worn it...knowing it clung to Metta’s hot legs...it made him feel so warm, boiling in the pit of his stomach. He rubbed the socks between his fingertips before he picked up the dress and sniffed it again, his magic slowly rising between his legs.

If he stopped to think, he’d surely scold himself, think about how disgusting this was. But with the dress and the socks and the scent and the image of Mettaton singing while wearing these very clothes, how could it not be exciting?

He contemplated this, touching the dress and playing with it before his eyes settled on the panties that laid in the laundry basket.

“O-oh…” Sans murmured, unable to think of anything else to say, picking it up. He slowly brought it to his face, sniffing it, the scent of Mettaton...these had touched the most private places, this should be horrifying, but no, it’s so arousing.

He imagines Mettaton, right in front of him, wearing the gown. His cheeks are flushed as he obediently begins to take off the outfit for his master.

“ _ Start with the socks, _ ” Sans would tell him. The king wouldn’t fight, he’d just nod and hike up his skirt, slowly pulling off the sock, bending and letting his panties show just for a second for only Sans. Only Sans.

When the socks were off, Metta would look back at him to ask what next, and Sans would point for the dress to come off. The moment it fell to the floor, he’d crook his fingers for Mettaton to come over, and the majestic king would eagerly walk over to him, standing right before the sitting jester. Sans would reach up and grab Mettaton’s ass, caressing and massaging, spanking it. Then he’d pull those panties off, rubbing Metta’s thick thighs all the way down. 

And when he bent back up, Metta would be as hard as Sans, except, he’d try to cover it with his hands, so Sans would just grab his hands and pin him to the bed.

He’d lean down, and press his teeth to Metta’s lips, parting them french kiss the boy. Feel his mouth. Metta’s such a slut, pouting his lip, just begging for someone to kiss those pretty little lips. He’d love it, squealing and moaning, driven senseless from the passionate kiss. Sans would pull away and the sexy little slut who cry out: “ _ Pl-please, take me, Sans! _ ” And Sans would slap his face and murmur: “ _ Prepare yourself, bitch.” _

And he’d lean back, watching the wet eyed, blushing Mettaton slip his fingers down past his eager cock, slipping his digits one by one inside, looking up at Sans. And Sans..he’d be rubbing his cock, watching the cute little king finger himself, begging and whimpering,  _ “hurry up and take me! Master, pl-please! _ ” And how could Sans resist someone who asked so nicely?

And then...Mettaton would be nice and hot and tight, begging for him, more and more, and Sans would give his little slut just what he needed, fast and hard and deep, until Metta was crying out and Sans was growling and groaning in his ear, and when they reached their limit, Metta would start gasping out his name.

_ “S-Sans, Sans!” _

“Oh, M-Metta~...Mettaton…” Sans gasped, head tilted back, working his cock in his hand, his hand tight just like Metta would be around him. “Mettaton~” and then he came, shivering and gasping, a whisper of the king’s names escaping him.

He stayed there, panting, hand in his pants, dress clutched in the other, snapping out of the bliss.

“F-fuck…” he murmured, looking down at the come covering his hand.

 

Metta got his clothing back, smiling when Sans gave him the folded clean clothing.

“Why, Sans~” he laughed. “I thought you were too lazy to clean clothing. 

“Well, you know~” he chuckled. “I couldn’t live with myself if I let my King down~”

Metta smirked and leaned down, kissing his forehead before chirping: “Off you go now~”

Sans left, cheeks flushed.

When Metta was putting the clothes away, he noticed his panties were gone.

Weird.


	3. Little Miss Muffet

**Summary for the Chapter:**

> Along came Muffet to see Mettaton  
> And sickly sweet things she would say  
> For too long the spider had sat down beside him  
> And the skeleton would make her pay.

**Notes for the Chapter:**

> Sorry for such a long absence. I lost inspiration for a while before something mildly angsty came to me. Spoil it? Probably won't, not yet. Hope you're enjoying it.

If you had told Mettaton that his loyal jester was obsessed with him, you would have ended up listening to his obnoxious laughter before he ordered the royal guards to take you away.

But to Sans, it would have been beautiful laughter. Gorgeous hypnotic laughter.

For really, was there was nothing more gorgeous than Mettaton.

People liked to say that no one really knew Mettaton, but that wasn't true. Napstablook knew Mettaton before he rose to power, when the star was just a delicate ghost with nothing more than a dream. Of course there was Alphys, who knew that, and had spent so much time with Mettaton.

But Sans knew everything.

If you knew Mettaton loved the colour purple, Sans knew Mettaton loved this specific shade of lavender. If you knew Mettaton sorted his socks by preference, Sans had the order memorised. If you knew Mettaton had a crush.

Sans knew exactly who they were. What they were doing, thinking, seeing at all times. Oh...he'd know. Their history, and their behaviours, he'd have them all written out.

Everything.

And also the most efficient manner of...disposing of them.

  
  


“Hello, your majesty, ufufu~” hummed the spider duchess, leaning down to kiss Mettaton’s hand.

“Hello, darling,” Mettaton responded, not even glancing up at her, too busy scrolling through the UnderNet.

Muffet tilted her head before she sat down at the edge of the couch. She took a moment to process the scene. The gorgeous King, his nails being painted by his loyal servant, a grudging cat named Burgerpants. Why he ever got such an odd name, she didn't know, but she never bothered to ask. He was, after all, only a servant. And her eyes were only for Mettaton. Thank god she had five of them to see him with.

Muffet liked to brag she could always find the best prey with her five big eyes. 

Sans didn't need five eyes to find a piece of prey. He had already found one with just two.

And of course, touching Mettaton like that was not allowed. Muffet was not WORTHY of the king’s godlike touch, to feel his delicious gaze.

As you know, attention from Mettaton was punishable by death in Sans’s book.

 

A long time ago, Papyrus had been in his home, sleeping in his race car bed, perfectly content, when he decided it was time for a drink. The skeleton stood up and put on his nightcap, as it was improper to walk around at night with your skull exposed, and began the walk downstairs. Oddly enough…

He heard the Washing Your Hands with Mettaton™ jingle.

Huh, that's strange. He thought he had turned the television off.

Oh, Papyrus! he had thought to himself. You giddy goat! You must have left the television on!

So he got to the bottom of the steps, taking a second to watch the screen.

_ “Hello, beauties!”  _ Mettaton exclaimed, posing. His new form- MTT EX, was it called? -was on the screen, washing his hands. The screen was close up on his hands.

His hands.

His hands.

Lathering, squeezing, slick with soap and moving with such direction. The sound was so loud, as if Mettaton was in the room.

Something stirred in Papyrus’s pants. He looked down, seeing a faint orange glow and a bulge.

“GA!” he shouted out in surprise. “SANS, THE TUMOUR IS BACK!”

Oddly, Sans did not come rushing down from upstairs, he sat up on the couch, pocketing his hands, pulling his pants up.

Papyrus didn't notice it, but the squeezing, slick, lathering sound had stopped.

“P-Pap?” Sans murmured, a bit dazed. “What's up?”

“Sans, there is a most unwelcome tumour in my pelvis! And...why are you watching Washing Your Hands with Mettaton™? Its quite late at night for this kind of entertainment.”

“Heh...well,  _ shower _ you doing, bro?”

Pap’s disgust at the pun was loudly announced by said skeleton, and the “tumour” disappeared.

_ If Papyrus had only put two and two together...he could have stopped the first murder. _

 

“Hey, Spidergirl,” Sans called, walking into the kitchen.

Muffet looked up, chuckling faintly. Before this, she had hated Sans, after all...it was true people were quite rich in Hotlands, and they liked expensive treats, but Sans sold his disgusting hot dogs and hot cats at such a low price...it would have surely put Muffet out of business before she got a career as the royal baker. However, now they both knew Muffet was the superior baker and Sans was just a flop at cooking.

But of course, Muffet wasn’t the only one in the kitchen. Grillby was there too, his flames flickering around as he cooked. He acknowledged Sans with a nod before going back to work.

“Hello, Sans,” she cooed, setting down her bowl. Some of the spiders in her cookie dough crawled away while she looked at him. “Did you need something?”

“Yeah, just one little thing,” he said, glancing around.

“Mm? What is it~?”

She only had a few seconds to notice the way his eye seemed to blaze blue and gold before a bone pierced her stomach.

Muffet gasped as pale blue blood began to spring up from her lips, moving down her jaw, dripping onto the ground.

Into the batter.

Then she fell.

Her vision blurred, watching as the flickering form of Grillby rushed towards Sans. What was happening..? It seemed that Sans was..and then...water rushed onto the ground, and Grillby sputtered out.

It only took a few minutes for Muffet to slip out of consciousness too.

 

It happened so fast, so quickly, Sans couldn’t understand why he had been so...so QUICK and vIOLENT. And why kill Grillby?! Grillby was such a nice fellow, he did-...did…

Sans sweeped up the white powder.

Not today.

Not today…

 

“MUFFET?!” cried out Mettaton, storming through the palace, trying to find the head baker. “Where is that damn spider?! I wanted my breakfast an hour ago!”

He slammed open the doors to the kitchen, ready to attack, when...oh.

The kitchen was tidy, empty, with just little note resting on the table.

Mettaton curiously opened it, reading it. It was in the spider girl’s gorgeous cursive handwriting.

 

_ Dear Mettaton,  _

_ I have had a wonderful experience working at New Home and MTT Resort these past years. As a result, it is a bittersweet occasion that I write to you this morning, announcing my resignation from the staff and my position as Head Baker. I leave in order to pursue Innkeeping as a full-time profession in Snowdin, a dream of mine for many years, and Grillby’s coming too. I appreciate and value the lessons I learned under your care. Thank you for the opportunities, the mentorship, and the support during these years—it was truly a joy. _

_ Fufufu, _

_ Muffet _

 

Mettaton was quiet for a moment. Then he got the odd feeling he was being watched, turning around.

But Sans was already gone.

 

Mettaton called a staff meeting the next day.

The heads of the New Home Royal Guard sat at one table. Asgore, Undyne, Papyrus. The Royal Guard was a huge group spread out over the Underground. In Snowdin, Endogeny, an amalgamate made of many wise old dogs, led a pack coolly and confidently. In Waterfall, the Temmies led a...er...well...I don’t think anyone told them they were part of the Royal Guard. In the Hotlands, 01 and 02 led a pleasant group of monsters who honestly preferred to chitchat rather than kill.

However, the three guards at the table were dangerous weapons.

Asgore, Head of the Royal Guard, the former king, a depressed old boss monster who bottled up his rage and unleashed it in battle.

Baroness Undyne of Waterfall, first in command of the Royal Guard, passionate and harsh in her actions.

Sir Papyrus, second in command of the Royal Guard, and…

Er…

Well.

He could make pasta.

Which I suppose is why Mettaton called the meeting in the first place.

To appoint Papyrus as the royal chef.

It was something Sans suggested, and Mettaton thought it was a good idea.

After all, Sans was his most loyal servant and had the best guidance.

Sans would never act impulsively.

Sans was a true moral person.

Well.

He’d learn the truth eventually. But not in a pleasant way.


	4. Cooking with Papyrus

**Summary for the Chapter:**

> Sing a song of sixpence,  
> A pocket full of rye.  
> Inedible ingredients  
> Baked in a pie.  
> But the pie was shattered  
> With a chock and a ching  
> Wasn't that a dainty dish,  
> To set before the king?  
> The king was in the kitchen then,  
> Counting out his money;  
> Loving a little skeleton  
> With a heart sweeter than honey  
> The jester was in the doorway  
> Watching real close  
> But he'd never kill that little one  
> Because they were bros.

**Notes for the Chapter:**

> The next chapter will be highly depressing. So I just wanted to leave this here uwu
> 
> Thank you so much for the comments, guys! You have no idea how much motivation they give me to keep writing this!

Mettaton tried Papyrus’s food, yes. But that doesn’t mean he enjoyed it.

There was a certain quality that Papyrus’s cooking had that Mettaton had never tasted before. It was new, and it made every bite feel like he was on the edge of dying.

That quality could only be described as “any redeeming qualities”.

So the king stormed down to the kitchen, his cloak sweeping out behind him, determined to get to the bottom of this. She’d have him fired in seconds.

Only to open the door and see him standing there, working away.

He was humming Bonetrousle and stirring the batter, swaying slightly as he went. He wore a bright pink apron with hearts over it and a puffy white chef hat, looking so damn cute…

On the television was a replay of one of Mettaton’s old episodes.

Mettaton only now noticed that Papyrus had done his best to dress like the Mettaton on the telly.

“Let’s see…” Papyrus murmured, looking at his ingredients. “Flour.” He set the entire bag in the bowl. “Milk.” He set the carton in the bowl. “And eggs.” He placed each egg in the bowl. “And of course, MTT-Brand always convenient human soul flavour substitute!” he sprinkled the liquid on top of the bag, carton, and eggs.

Mettaton let out a laugh at this, tilting his head and giggling. He hadn’t laughed this hard in a very long time.

Papyrus spun around, widening his eyes and immediately sweeping over into a bow.

“Y-YOUR MAJESTY, I HAD NO IDEA YOU WERE THERE!” he cried out, and in the process of sweeping into a bow, he sent the bowl flying and crashing to the ground.

Oops.

And that, to say the least, is when King Mettaton fell in love with the skeleton.


End file.
